U.S. patent number 10,079,417 [Application Number 15/614,640] was granted by the patent office on 2018-09-18 for high-frequency transmission line and electronic device.
This patent grant is currently assigned to Murata Manufacturing Co., Ltd.. The grantee listed for this patent is Murata Manufacturing Co., Ltd.. Invention is credited to Takahiro Baba, Nobuo Ikemoto, Satoshi Ishino, Noboru Kato, Jun Sasaki, Kuniaki Yosui.
United States Patent |
10,079,417 |
Kato , et al. |
September 18, 2018 |
High-frequency transmission line and electronic device
Abstract
A transmission line portion of a flat cable includes first
regions and second regions connected alternately. In the first
region, the transmission line portion is a flexible tri-plate
transmission line including a dielectric element including a signal
conductor, a first ground conductor including opening portions, and
a second ground conductor which is a solidly filled conductor. In
the second region, the transmission line portion is a hard
tri-plate transmission line including a wide dielectric element
including a meandering conductor, and a first ground conductor and
a second ground conductor which are solidly filled conductors. A
variation width of the characteristic impedance in the second
region is larger than a variation width of the characteristic
impedance in the first region.
Inventors: |
Kato; Noboru (Nagaokakyo,
JP), Ishino; Satoshi (Nagaokakyo, JP),
Sasaki; Jun (Nagaokakyo, JP), Yosui; Kuniaki
(Nagaokakyo, JP), Baba; Takahiro (Nagaokakyo,
JP), Ikemoto; Nobuo (Nagaokakyo, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Murata Manufacturing Co., Ltd. |
Nagaokakyo-shi, Kyoto-fu |
N/A |
JP |
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Assignee: |
Murata Manufacturing Co., Ltd.
(Kyoto, JP)
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Family
ID: |
49783225 |
Appl.
No.: |
15/614,640 |
Filed: |
June 6, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170271733 A1 |
Sep 21, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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15285625 |
Oct 5, 2016 |
9748625 |
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14564140 |
Nov 8, 2016 |
9490516 |
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PCT/JP2013/067594 |
Jun 27, 2013 |
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Foreign Application Priority Data
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Jun 28, 2012 [JP] |
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2012-144862 |
Jan 22, 2013 [JP] |
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2013-009105 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01P
3/082 (20130101); H01P 3/02 (20130101); H05K
1/0221 (20130101); H01P 3/085 (20130101); H05K
1/14 (20130101); H01P 5/00 (20130101); H05K
1/0237 (20130101); H05K 1/028 (20130101); H05K
1/0296 (20130101); H01P 3/08 (20130101); H01P
5/028 (20130101); H05K 2201/0707 (20130101); H05K
1/0242 (20130101); H05K 1/186 (20130101); H05K
3/361 (20130101); H01P 3/026 (20130101); H05K
1/025 (20130101); H05K 2201/09218 (20130101); H05K
1/0218 (20130101); H05K 1/148 (20130101); H01P
3/003 (20130101) |
Current International
Class: |
H05K
7/00 (20060101); H01P 3/08 (20060101); H01P
3/02 (20060101); H05K 1/02 (20060101); H05K
1/14 (20060101); H01P 5/00 (20060101); H01P
5/12 (20060101); H05K 1/18 (20060101); H05K
5/00 (20060101); H01P 5/02 (20060101); H01P
3/00 (20060101); H05K 3/36 (20060101) |
Field of
Search: |
;361/748,749,753,777,778,816,818 ;174/261 ;33/128,238,246 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Kato et al., "High-Frequency Transmission Line and Electronic
Device", U.S. Appl. No. 15/285,625, filed Oct. 5, 2016. cited by
applicant.
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Primary Examiner: Tran; Binh
Attorney, Agent or Firm: Keating & Bennett, LLP
Claims
What is claimed is:
1. A high-frequency transmission line comprising: a flexible planar
dielectric element elongated in one direction, the dielectric
element having a predetermined width in a direction perpendicular
or substantially perpendicular to a longitudinal direction and
having a predetermined thickness; a signal conductor disposed in
the dielectric element and configured to extend along the
longitudinal direction; and a first ground conductor opposing the
signal line conductor and extending in the longitudinal direction;
wherein at least one of the signal conductor and the first ground
conductor has a characteristic impedance cyclically varied along
the longitudinal direction, and includes a first region and a
second region with different variation widths of the characteristic
impedance; the variation width of the characteristic impedance in
the second region is larger than the variation width of the
characteristic impedance in the first region; the second region is
provided at a plurality of locations along the longitudinal
direction, and a plurality of the second regions have the same or
substantially the same variation width of the characteristic
impedance; at least three of the second regions are located at
equal or substantially equal intervals in the longitudinal
direction; and the characteristic impedance in the first region is
varied in cycles.
2. The high-frequency transmission line according to claim 1,
wherein in the first region, the first ground conductor is
configured to extend along the longitudinal direction, and includes
two elongated conductors disposed at both ends in the width
direction with a space between each other and configured to extend
in the longitudinal direction, and a plurality of bridge conductors
that connect between the two elongated conductors at intervals
along the longitudinal direction.
3. The high-frequency transmission line according to claim 2,
wherein the second region is configured to rotate a phase of a
high-frequency signal by a predetermined amount through
transmission between an input end and an output end.
4. The high-frequency transmission line according to claim 3,
wherein in the second region, the signal conductor is a conductor
line with a length that rotates the phase of the high-frequency
signal by the predetermined amount and the first ground conductor
is a conductor arranged to extend over an entirety or substantially
the entirety of one end surface of the dielectric element.
5. The high-frequency transmission line according to claim 3,
further comprising: a third ground conductor provided in the second
region and located at or substantially at a same position as the
signal conductor in a thickness direction, the third ground
conductor being configured to extend in parallel or substantially
in parallel with the signal conductor with a constant or a
substantially constant gap therebetween, and the third ground
conductor being connected to the first ground conductor.
6. The high-frequency transmission line according to claim 1,
wherein a width of the second region is larger than a width of the
first region.
7. The high-frequency transmission line according to claim 1,
further comprising a second ground conductor opposite to the first
ground conductor with the signal conductor interposed
therebetween.
8. The high-frequency transmission line according to claim 1,
further comprising a connector member configured to be connected to
the signal conductor provided at at least one end in the
longitudinal direction.
9. An electronic device comprising: the high-frequency transmission
line according to claim 1; a plurality of circuit boards connected
to each other by the high-frequency transmission line; and a
housing that houses the circuit boards.
10. The electronic device according to claim 9, wherein the
high-frequency transmission line is bent at at least one location
in the first region.
11. The electronic device according to claim 9, wherein in the
first region, the first ground conductor is configured to extend
along the longitudinal direction, and includes two elongated
conductors disposed at both ends in the width direction with a
space between each other and configured to extend in the
longitudinal direction, and a plurality of bridge conductors that
connect between the two elongated conductors at intervals along the
longitudinal direction.
12. The electronic device according to claim 11, wherein the second
region is configured to rotate a phase of a high-frequency signal
by a predetermined amount through transmission between an input end
and an output end.
13. The electronic device according to claim 12, wherein in the
second region, the signal conductor is a conductor line with a
length that rotates the phase of the high-frequency signal by the
predetermined amount and the first ground conductor is a conductor
arranged to extend over an entirety or substantially the entirety
of one end surface of the dielectric element.
14. The electronic device according to claim 12, further
comprising: a third ground conductor provided in the second region
and located at or substantially at a same position as the signal
conductor in a thickness direction, the third ground conductor
being configured to extend in parallel or substantially in parallel
with the signal conductor with a constant or a substantially
constant gap therebetween, and the third ground conductor being
connected to the first ground conductor.
15. The electronic device according to claim 9, wherein a width of
the second region is larger than a width of the first region.
16. The electronic device according to claim 9, wherein the second
region is provided at a plurality of locations along the
longitudinal direction, and a plurality of the second regions have
the same or substantially the same variation width of the
characteristic impedance.
17. The electronic device according to claim 9, further comprising
a second ground conductor opposite to the first ground conductor
with the signal conductor interposed therebetween.
18. The electronic device according to claim 9, further comprising
a connector member configured to be connected to the signal
conductor provided at least one end in the longitudinal
direction.
19. The high-frequency transmission line according to claim 1,
wherein in the first region, opening portions of the first ground
conductor are provided at predetermined intervals.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thin high-frequency transmission
line for transmission of a high-frequency signal and an electronic
device including the high-frequency transmission line.
2. Description of the Related Art
Typical examples of a high-frequency line for transmission of a
high-frequency signal according to the related art include a
coaxial cable. The coaxial cable includes a center conductor
(signal conductor) configured to extend in one direction
(configured to extend in the signal transmission direction), and a
shield conductor provided concentrically along the outer peripheral
surface of the center conductor.
In recent years, high-frequency devices including mobile
communication terminals have been reduced in size and thickness,
and a space for arrangement of the coaxial cable may not be secured
in a terminal housing. In addition, the coaxial cable is hard, and
thus not easily curved or bent to be routed.
Use of high-frequency transmission lines described in International
Publication No. 2011/007660 and Japanese Registered Utility Model
No. 3173143 is drawing attention to solve a problem that occurs
when such a coaxial cable is utilized. The high-frequency
transmission line is larger in width than the coaxial cable but can
be thinned, and therefore is particularly useful in the case where
there is only a small clearance in the terminal housing. In
addition, the high-frequency transmission line has a flexible
dielectric element as the base material, and thus is flexible and
can be easily curved and bent to be routed.
The high-frequency transmission lines described in International
Publication No. 2011/007660 and Japanese Registered Utility Model
No. 3173143 have a tri-plate strip line structure as the basic
structure.
The high-frequency transmission lines described in International
Publication No. 2011/007660 and Japanese Registered Utility Model
No. 3173143 include a flat-plate dielectric element that is
flexible and insulating. The dielectric element has an elongated
shape that extends straight. A second ground conductor is disposed
on a second surface orthogonal to the thickness direction of the
dielectric element. The second ground conductor has a so-called
solidly filled conductor pattern in which the second surface of the
base material sheet is covered generally entirely. A first ground
conductor is disposed on a first surface of the base material sheet
opposite to the second surface. The first ground conductor includes
elongated conductors configured to extend along the longitudinal
direction at both ends in the width direction orthogonal to the
longitudinal direction and the thickness direction. The two
elongated conductors are connected to each other by bridge
conductors disposed at predetermined intervals along the
longitudinal direction and configured to extend in the width
direction. Thus, the first ground conductor is shaped such that
opening portions with a predetermined opening length are formed and
arranged along the longitudinal direction.
A signal conductor with a predetermined width and a predetermined
thickness is formed in the middle of the dielectric element in the
thickness direction. The signal conductor is elongated to extend in
the direction parallel with the elongated conductor portions of the
first ground conductor and the second ground conductor. The signal
conductor is formed generally in the center of the dielectric
element in the width direction.
When the thus configured high-frequency transmission line is viewed
in plan (seen from a direction orthogonal to the first surface and
the second surface), the signal conductor is disposed so as to
overlap the first ground conductor only at the bridge conductors
and be provided in the opening portions in other regions.
With such a shape, the high-frequency transmission lines having
predetermined transmission characteristics can be thinned, and can
be easily curved and bent to be routed. The terms "curve" and
"bend" as used herein refer to three-dimensional deformation that
causes the entire flat-plate surface of the high-frequency
transmission lines not to be present on an identical plane. In
other words, the terms relate to causing a bend by a predetermined
angle with respect to the flat-plate surface of the high-frequency
transmission lines.
However, the high-frequency transmission lines structured as
discussed above have the following problem. FIGS. 14A and 14B are
each a graph illustrating the distribution characteristics of
characteristic impedance for explaining the problem with the
high-frequency transmission line structured in accordance with the
related art.
In the high-frequency transmission line according to the related
art, the first ground conductor includes a plurality of opening
portions provided along the longitudinal direction. Thus, the first
ground conductor and the signal conductor face each other along the
thickness direction only at the locations of installation of the
bridge conductors. Therefore, a C property (capacitive property)
becomes highest at the positions of the bridge conductors along the
longitudinal direction, and an L property (inductive property)
becomes highest in the middle of the opening portions.
Since the bridge conductors are disposed at predetermined intervals
as discussed above, the characteristic impedance of the
high-frequency transmission line according to the related art is
cyclically varied in accordance with the interval of installation
of the bridge conductors. Setting is made such that a desired
characteristic impedance is obtained for the overall length of the
high-frequency transmission line.
The characteristic impedance is set with the high-frequency
transmission line not curved. Thus, with the high-frequency
transmission line not curved, as illustrated in FIG. 14A, the
characteristic impedance is varied in accordance with the interval
of installation of the bridge conductors, and a desired
characteristic impedance Zo is obtained for the overall length. In
this event, the amplitude .DELTA.R0 of the real number of the
characteristic impedance has a constant value.
In the case where the high-frequency transmission line is curved,
however, the positional relationship between the signal conductor
and the first ground conductor and the second ground conductor is
varied at curved portions. In this case, the characteristic
impedance at the curved portions is varied. Depending on the curved
state, as illustrated in FIG. 14B, for example, the L property in
an opening portion may be increased such that the amplitude
.DELTA.R0' of the real number of the characteristic impedance at
the curved portions is larger than the amplitude .DELTA.R0 of the
real number of the characteristic impedance at non-curved
portions.
The characteristic impedance for the entire high-frequency
transmission line greatly depends on the maximum value of the
amplitude of the real number of the characteristic impedance. Thus,
if the high-frequency transmission line is curved and the maximum
value of the amplitude of the real number of the characteristic
impedance is varied, the characteristic impedance for the entire
high-frequency transmission line is also varied. For example, as
illustrated in FIG. 14B, the characteristic impedance Z0' of the
entire high-frequency transmission line with curved portions is
different from the characteristic impedance Z0 of the entire
high-frequency transmission line which is not curved. Therefore,
the transmission loss of an RF signal may be increased to degrade
the transmission characteristics.
SUMMARY OF THE INVENTION
Preferred embodiments of the present invention provide a
high-frequency transmission line with an overall characteristic
impedance that is hardly varied even if the high-frequency
transmission line is partly curved in the thickness direction, and
an electronic device.
A high-frequency transmission line according to a preferred
embodiment of the present invention includes a dielectric element,
a signal conductor, and a first ground conductor. The dielectric
element is a flexible flat plate elongated in one direction, the
flat plate having a predetermined width in a direction
perpendicular or substantially perpendicular to a longitudinal
direction and having a predetermined thickness. The signal
conductor is disposed in the dielectric element, and configured to
extend along the longitudinal direction. The first ground conductor
opposes the signal line conductor and extends in the longitudinal
direction.
At least one of the signal conductor and the first ground conductor
has a characteristic impedance cyclically varied along the
longitudinal direction, and includes a first region and a second
region with different variation widths of the characteristic
impedance. The variation width of the characteristic impedance in
the second region is larger than the variation width of the
characteristic impedance in the first region.
According to the configuration, the characteristic impedance in the
second region is dominant in the characteristic impedance of the
entire high-frequency transmission line. Thus, the characteristic
impedance for the entire high-frequency transmission line is hardly
varied if the first region is bent, because the characteristic
impedance in the second region is not varied although the
characteristic impedance in the first region is varied.
A high-frequency transmission line according to a preferred
embodiment of the present invention is preferably configured as
follows. In the first region of the high-frequency transmission
line, the first ground conductor is configured to extend along the
longitudinal direction, and configured to include two elongated
conductors disposed at both ends in the width direction with a
space between each other and configured to extend in the
longitudinal direction, and a plurality of bridge conductors that
connect between the two elongated conductors at intervals along the
longitudinal direction. The second ground conductor is a conductor
arranged to extend generally over the entire other end surface.
The configuration indicates a specific example of the configuration
of the first region of the high-frequency transmission line. With
such a configuration, the first ground conductor is structured such
that a plurality of opening portions in which a conductor is not
provided are arranged along the longitudinal direction. Thus, the
proportion of the conductor occupying the first region is reduced
compared to the dielectric element, which enables the first region
to be easily curved or bent.
The second region of the high-frequency transmission line according
to a preferred embodiment of the present invention is preferably
configured so as to rotate a phase of a high-frequency signal by a
predetermined amount through transmission between an input end and
an output end.
According to the configuration, the second region further functions
as a phase adjustment circuit. Thus, the input high-frequency
signal is capable of being transmitted by the high-frequency
transmission line to be output with a predetermined phase.
The high-frequency transmission line according to a preferred
embodiment of the present invention is preferably configured as
follows. In the second region of the high-frequency transmission
line, the signal conductor is a conductor line with such a length
that rotates the phase of the high-frequency signal by the
predetermined amount. In the second region of the high-frequency
transmission line, the first ground conductor is a conductor
arranged to extend generally over the entire one end surface of the
dielectric element.
According to the configuration, the second region of the
high-frequency transmission line is implemented by a distributed
constant line. Thus, the second region is configured to function as
a phase adjustment circuit (delay line) with good frequency
characteristics. In addition, the first ground conductor and the
second ground conductor are so-called solidly filled conductors,
which can make the second region harder and difficult to be curved
or bent.
A high-frequency transmission line according to a preferred
embodiment of the present invention is preferably configured as
follows. The high-frequency transmission line further includes a
third ground conductor provided in the second region of the
high-frequency transmission line and arranged generally at the same
position as the signal conductor in the thickness direction, the
third ground conductor being configured to extend in parallel or
substantially in parallel with the signal conductor with a
generally constant gap therebetween, and the third ground conductor
being connected to the first ground conductor at high
frequencies.
According to the configuration, the conductor line constituting the
phase adjustment circuit is surrounded by a ground. Thus, the
characteristics of the phase adjustment circuit are capable of
being set highly precisely, and a desired amount of phase rotation
is achieved highly precisely.
In the high-frequency transmission line according to a preferred
embodiment of the present invention, a width of the second region
is preferably larger than a width of the first region.
According to the configuration, the second region has a large area,
which makes the second region hard and difficult to be curved or
bent.
The high-frequency transmission line according to a preferred
embodiment of the present invention is preferably configured as
follows. The second region of the high-frequency transmission line
is provided at a plurality of locations along the longitudinal
direction of the high-frequency transmission line, and a plurality
of such second regions have generally the same variation width of
the characteristic impedance.
According to the configuration, the plurality of second regions
which are not curved or bent have generally the same characteristic
impedance, which further stabilizes the characteristic impedance
for the entire high-frequency transmission line.
A high-frequency transmission line according to a preferred
embodiment of the present invention preferably further includes a
second ground conductor disposed opposite to the first ground
conductor with the signal conductor interposed therebetween.
Thus, a tri-plate transmission line is provided.
A high-frequency transmission line according to a preferred
embodiment of the present invention preferably further include a
connector member for connection to the signal conductor provided at
at least one end in the longitudinal direction.
According to the configuration, the connector member is configured
so that the high-frequency transmission line is easily connected to
an external circuit board or the like.
Another preferred embodiment of the present invention provides an
electronic device including any high-frequency transmission line
according to the various preferred embodiments of the present
invention discussed above, a plurality of circuit boards connected
to each other by the high-frequency transmission line, and a
housing that houses the circuit boards.
According to the configuration, the electronic device includes one
of the high-frequency transmission lines described above. Use of
the high-frequency transmission line discussed above allows
transmission of a high-frequency signal between the circuit boards
without increasing a transmission loss even if the high-frequency
transmission line is used as curved or bent.
In an electronic device according to a preferred embodiment of the
present invention, the high-frequency transmission line is
preferably bent at least one location in the first region.
According to the configuration, arrangement modes of the
high-frequency transmission line are increased. Further, the
characteristic impedance of the high-frequency transmission line is
constant in whichever arrangement mode is adopted to bend the
high-frequency transmission line. Thus, the transmission
characteristics for a high-frequency signal within the electronic
device are improved.
According to various preferred embodiments of the present
invention, the characteristic impedance for the entire flat cable
is hardly varied even if the flat cable is partly curved. Thus, a
flat cable with stable transmission characteristics that are not
affected by the mode of use is provided.
The above and other elements, features, steps, characteristics and
advantages of the present invention will become more apparent from
the following detailed description of the preferred embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A to 1C are each a perspective view illustrating the
appearance of a flat cable according to a first preferred
embodiment of the present invention.
FIG. 2 is an exploded perspective view illustrating the structure
of a first region of a transmission line portion of the flat cable
according to the first preferred embodiment of the present
invention.
FIG. 3 is an exploded perspective view illustrating the structure
of a second region of the transmission line portion of the flat
cable according to the first preferred embodiment of the present
invention.
FIGS. 4A and 4B are each a graph illustrating the distribution
characteristics of characteristic impedance along the longitudinal
direction of the transmission line portion of the flat cable
according to a preferred embodiment of the present invention.
FIGS. 5A and 5B are a side sectional view and a plan sectional
view, respectively, illustrating the partial configuration of a
portable electronic device according to the first preferred
embodiment of the present invention.
FIG. 6 is an exploded perspective view illustrating the structure
of a second region of a transmission line portion of a flat cable
according to a second preferred embodiment of the present
invention.
FIG. 7 is a graph illustrating the distribution characteristics of
characteristic impedance along the longitudinal direction of the
transmission line portion of the flat cable according to the second
preferred embodiment of the present invention.
FIG. 8 is an exploded perspective view illustrating the structure
of a second region of a transmission line portion of a flat cable
according to a third preferred embodiment of the present
invention.
FIG. 9 is an exploded perspective view illustrating the structure
of a second region of a transmission line portion of a flat cable
according to a fourth preferred embodiment of the present
invention.
FIG. 10 is an exploded perspective view illustrating the structure
of a second region of a transmission line portion of a flat cable
according to a fifth preferred embodiment of the present
invention.
FIG. 11 is an exploded perspective view illustrating the structure
of a second region of a transmission line portion of a flat cable
according to a sixth preferred embodiment of the present
invention.
FIG. 12 is an exploded perspective view illustrating the structure
of a second region of a transmission line portion of a flat cable
according to a seventh preferred embodiment of the present
invention.
FIG. 13 is a perspective view illustrating the appearance of a flat
cable with a constant width.
FIGS. 14A and 14B are each a graph illustrating the distribution
characteristics of characteristic impedance for explaining a
problem caused with a flat cable structured in accordance with the
related art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A flat cable according to a first preferred embodiment of the
present invention will be described with reference to the drawings.
FIGS. 1A to 1C are each a perspective view illustrating the
appearance of a flat cable which is a high-frequency transmission
line according to the first preferred embodiment of the present
invention. FIG. 1A illustrates a state in which the flat cable is
not curved at all over the overall length. FIGS. 1B and 1C each
illustrate a state in which the flat cable is partly curved, the
flat cable being curved more greatly in FIG. 1C than in FIG. 1B. In
FIG. 1A, the side on which coaxial connectors are disposed is
defined as the upper surface. In FIGS. 1B and 1C, the side on which
the coaxial connectors are disposed is defined as the lower
surface.
FIG. 2 is an exploded perspective view illustrating the structure
of a first region of a transmission line portion of the flat cable
according to the first preferred embodiment of the present
invention. FIG. 3 is an exploded perspective view illustrating the
structure of a second region of the transmission line portion of
the flat cable according to the first preferred embodiment of the
present invention.
A flat cable 60 includes a transmission line portion 10 and coaxial
connectors 61. The transmission line portion 10 has a flat and
elongated shape. The transmission line portion 10 is configured
such that a first region 100S, a second region 100H, a first region
100S, a second region 100H, and a first region 100S are
continuously provided along the longitudinal direction.
Two coaxial connectors 61 are provided, and installed at both ends
of the transmission line portion 10 in the longitudinal direction.
The coaxial connectors 61 are installed on the side of a second
principal surface (corresponding to the other surface according to
the present invention) of the transmission line portion 10 via
conversion pedestals 62. A center conductor (not illustrated) of
the coaxial connector 61 is connected to an end portion of a signal
conductor 40 (see FIGS. 2 and 3) of the transmission line portion
10. Meanwhile, an outside conductor (not illustrated) of the
coaxial connector 61 is connected to a second ground conductor 30
of the transmission line portion 10. The coaxial connectors 61 and
the conversion pedestals 62 may be omitted, and arrangements other
than the coaxial arrangement may be adopted. In the case where the
coaxial connectors 61 and the conversion pedestals 62 are omitted,
portions of the signal conductor 40 around both ends of the
transmission line portion 10 or a first ground conductor 20 and the
second ground conductor 30 may be exposed to the outside. In
addition, the coaxial connectors may be installed on different
surfaces. For example, the coaxial connector 61 at one end may be
installed on the side of the first principal surface, and the
coaxial connector 61 at the other end may be installed on the side
of the second principal surface.
As illustrated in FIGS. 1A to 1C, the transmission line portion 10
has an appearance in which a flat dielectric element 110 is
sandwiched between a protective layer 120 and a protective layer
130 from both sides in the thickness direction of the dielectric
element 110. Specifically, the protective layer 130 is arranged to
extend generally over the entire surface of the dielectric element
110 on the side of the first principal surface which is an end
surface of the dielectric element 110 on one side in the thickness
direction. The protective layer 120 is arranged to extend generally
over the entire surface of the dielectric element 110 on the side
of the second principal surface which is an end surface of the
dielectric element 110 on the other side in the thickness
direction.
A specific structure of the first region 100S and the second region
100H constituting the transmission line portion 10 will be
described next.
The first region 100S includes the dielectric element 110 including
a first dielectric layer 111 and a second dielectric layer 112. The
dielectric element 110 is a flexible flat plate having a
predetermined thickness. The dielectric element 110 is elongated in
a first direction along a flat-plate surface, and has a
predetermined width in a direction along the flat-plate surface and
perpendicular or substantially perpendicular to the longitudinal
direction (first direction). The dielectric element 110 is
preferably made of a flexible material such as polyimide or a
liquid crystal polymer, for example.
The signal conductor 40 has a flat-film shape, and is provided
between the first dielectric layer 111 and the second dielectric
layer 112. The signal conductor 40 is preferably located generally
in the center of the dielectric element 110 in the width direction.
The width of the signal conductor 40 is smaller than the width of
the dielectric element 110. More specifically, the width of the
signal conductor 40 is smaller than the gap, in the width
direction, between elongated conductors 21 and 22 constituting the
first ground conductor 20 to be discussed later. The signal
conductor 40 is preferably located in the middle of the dielectric
element 110 in the thickness direction. The position of the signal
conductor 40 in the thickness direction is set such that a
characteristic impedance desired for the transmission line portion
10 is obtained. In other words, the thickness of first dielectric
layer 111 and the second dielectric layer 112 is set such that a
characteristic impedance desired for the transmission line portion
10 is obtained. The signal conductor 40 preferably is made of a
highly electrically conductive material such as copper (Cu), for
example.
The first ground conductor 20 is provided on the first principal
surface (surface on the side of the first dielectric layer 111) of
the dielectric element 110. However, if desired, the first ground
conductor 20 may be provided in the dielectric element 110. The
first ground conductor 20 includes the elongated conductors 21 and
22 and bridge conductors 23. The first ground conductor 20
preferably is also made of a highly electrically conductive
material such as copper (Cu), for example.
The elongated conductors 21 and 22 have an elongated shape to
extend along the longitudinal direction of the dielectric element
110. The elongated conductor 21 is preferably located at one end of
the dielectric element 110 in the width direction. The elongated
conductor 22 is preferably located at the other end of the
dielectric element 110 in the width direction. The elongated
conductors 21 and 22 are arranged with a predetermined gap
therebetween along the width direction of the dielectric element
110.
The bridge conductors 23 are configured to extend in the width
direction of the dielectric element 110. A plurality of bridge
conductors 23 are arranged at intervals along the longitudinal
direction of the dielectric element 110. Thus, opening portions 24
are located between the bridge conductors 23 as seen in the
direction perpendicular or substantially perpendicular to the first
principal surface (as seen along the thickness direction).
In this way, the first ground conductor 20 preferably has a ladder
shape to extend in the longitudinal direction.
The second ground conductor 30 is provided on the second principal
surface (surface on the side of the second dielectric layer 112) of
the dielectric element 110. The second ground conductor 30 is
arranged to extend generally over the entire surface of the
dielectric element 110. The second ground conductor is also
preferably made of a highly electrically conductive material such
as copper (Cu), for example.
The first ground conductor 20 and the second ground conductor 30
are connected to each other by connection conductors 50. The
connection conductors 50 are so-called electrically conductive via
conductors, and penetrate the dielectric element 110 in the
thickness direction. The connection conductors 50 are provided at
positions of the first ground conductor 20 at which the elongated
conductors 21 and 22 and the bridge conductors 23 are connected to
each other.
In the thus configured first region 100S of the transmission line
portion 10, the signal conductor 40 provided in the dielectric
element 110 is sandwiched between the first ground conductor 20 and
the second ground conductor 30. Thus, a so-called tri-plate
transmission line is provided. In this case, the second ground
conductor 30 which is a solidly filled conductor defines and serves
as a reference ground, and the first ground conductor 20 with a
ladder shape defines and serves as an auxiliary ground.
In the first region 100S, opening portions in which no conductor is
provided are arranged at predetermined intervals along the
longitudinal direction. Thus, for the first region 100S, the
proportion of the conductor to the dielectric element 110 is
lowered and the thickness of the dielectric element is reduced
compared to a case where the first ground conductor is a solidly
filled electrode as with the second ground conductor. Thus, the
first region 100S is flexible, and is capable of being easily bent
at a predetermined angle in the thickness direction with respect to
a flat-plate surface of the flat cable.
The second region 100H includes a dielectric element 110H including
a first dielectric layer 111H and a second dielectric layer 112H.
The dielectric element 110H is a flexible flat plate having a
predetermined thickness. The dielectric element 110H is preferably
wider than the dielectric element 110 of the first region 100S. The
width of the dielectric element 110H may be about the same as the
width of the dielectric element 110 of the first region 100S.
The dielectric element 110H is preferably made of a flexible
material such as polyimide or a liquid crystal polymer, for
example. The first dielectric layer 111H is preferably integral
with the first dielectric layer 111 of the first region 100S. The
second dielectric layer 112H is preferably integral with the second
dielectric layer 112 of the first region 100S. That is, the
dielectric element 110H of the second region 100H is preferably
integral with the dielectric element 110 of the first region
100S.
The second region 100H includes a meandering conductor 40H. The
meandering conductor 40H is located between the first dielectric
layer 111H and the second dielectric layer 112. Both ends of the
meandering conductor 40H are connected to the signal conductor 40
of the first region 100S connected to the second region 100H. The
meandering conductor 40H defines and functions as an inductor
connected in series with a transmission line in a distributed
constant circuit. The length of the meandering conductor 40H is set
such that the phase of a high-frequency signal transmitted through
the meandering conductor 40H is rotated by a desired phase amount.
Use of such an inductor for a distributed constant circuit provides
a phase adjustment circuit with good frequency characteristics that
causes no variation in inductance according to the frequency. Thus,
a transmission signal is transmitted with a low loss even in the
case where the transmission signal has a predetermined frequency
band.
The second region 100H includes a first ground conductor 20H. The
first ground conductor 20H is provided on the first principal
surface (surface on the side of the first dielectric layer 111H) of
the dielectric element 110H. The first ground conductor 20H is
arranged to extend generally over the entire first principal
surface of the dielectric element 110H. That is, the first ground
conductor 20H is a solidly filled conductor in the second region
100H. The first ground conductor 20H is also made of a highly
electrically conductive material such as copper (Cu), for example.
The first ground conductor 20H is preferably integral with the
first ground conductor 20 of the first region 100S.
The second region 100H includes a second ground conductor 30H. The
second ground conductor 30H is provided on the second principal
surface (surface on the side of the second dielectric layer 112H)
of the dielectric element 110H. The second ground conductor 30H is
arranged to extend generally over the entire second principal
surface of the dielectric element 110H. That is, the second ground
conductor 30H is a solidly filled conductor in the second region
100H. The second ground conductor 30H is also preferably made of a
highly electrically conductive material such as copper (Cu), for
example. The second ground conductor 30H is preferably integral
with the second ground conductor 30 of the first region 100S.
The first ground conductor 20H and the second ground conductor 30H
are connected to each other by connection conductors 50H. The
connection conductors 50H are so-called electrically conductive via
conductors, and penetrate the dielectric element 110H in the
thickness direction. A plurality of connection conductors 50H are
provided in regions excluding a region in which the meandering
conductor 40H is arranged to define the second region 100H is
viewed in plan.
The thus configured second region 100H defines and functions as a
phase adjustment circuit that rotates the phase of a high-frequency
signal by a predetermined phase amount when the high-frequency
signal is transmitted between adjacent first regions 100S connected
to each other. Thus, a high-frequency signal input to the flat
cable 60 is output after being adjusted to a predetermined phase.
The second region 100H may be provided with a coil-shaped inductor
pattern or capacitor pattern, and may be configured to define and
function as a filter circuit such as a low-pass filter or a
high-pass filter. In the case where a coil-shaped inductor pattern
is provided, the impedance of the second region 100H is easily
increased compared to the impedance at positions at which the
bridge conductors 23 are located.
Further, the second region 100H according to the present preferred
embodiment includes third ground conductors 41. The third ground
conductors 41 are provided between the first dielectric layer 111H
and the second dielectric layer 112H. In other words, the third
ground conductors 41 are provided at the same position as the
meandering conductor 40H along the thickness direction of the
dielectric element 110H. The third ground conductors 41 are
provided at a predetermined distance from the meandering conductor
40H to extend in parallel or substantially in parallel with the
meandering conductor 40H. The third ground conductors 41 are
connected to the first ground conductor 20H and the second ground
conductor 30H by the connection conductors 50H. With such a
configuration, the characteristics of the phase adjustment circuit
implemented by the second region 200H are capable of being set
highly precisely. Thus, a predetermined amount of phase rotation is
capable of being provided to a high-frequency signal with higher
precision. Further, the meandering conductor 40H is shielded from
the external environment. Thus, leakage of extraneous radiation
generated by the meandering conductor 40H to the outside is
significantly reduced or prevented.
With the configuration according to the present preferred
embodiment, in addition, in the second region 100H, the meandering
conductor 400H is sandwiched between solidly filled conductors, and
thus the proportion of the conductor to the dielectric element is
increased. Thus, the second region 100H is harder than the first
region 100S, and is difficult to be bent. With the configuration
according to the preferred embodiment described above, further, the
width of the second region 100H is larger than the width of the
first region 100S, which makes the second region 100H harder and
even more difficult to be bent.
When such a configuration is used, the transmission line portion 10
of the flat cable 60 has the following distribution characteristics
of characteristic impedance along the longitudinal direction. FIGS.
4A and 4B are each a graph illustrating the distribution
characteristics of characteristic impedance along the longitudinal
direction of the transmission line portion 10 of the flat cable 60
according to the present preferred embodiment. FIG. 4A illustrates
a state with no bend. FIG. 4B illustrates a state in which the
first region 100S is bent.
In the first region 100S, the characteristic impedance is varied in
cycles matching the interval of arrangement of the bridge
conductors 23. Specifically, the characteristic impedance becomes
minimum with the C property enhanced at positions of the bridge
conductors 23 along the longitudinal direction, at which the bridge
conductors 23 and the signal conductor 40 face each other in the
thickness direction. The characteristic impedance becomes maximum
with the L property enhanced most at positions between the bridge
conductors 23 along the longitudinal direction, in other words, at
the center positions of the opening portions 24 along the
longitudinal direction. Thus, the variation width of the
characteristic impedance, which is the difference between the
maximum value and the minimum value of the characteristic
impedance, in the first region 100S is .DELTA.R0.
In the second region 100H, the meandering conductor 40H is
preferably used, and thus the characteristic impedance becomes
maximum with the L property enhanced most at the middle position in
the extending direction of the meandering conductor 40H. On the
other hand, the characteristic impedance becomes minimum with the C
property enhanced at the boundary position between the second
region 100H and the first region 100S, at which the signal
conductor 40 and the first ground conductor 20H face each other.
Thus, the variation width of the characteristic impedance, which is
the difference between the maximum value and the minimum value of
the characteristic impedance, in the second region 100H is
.DELTA.R1.
In this event, the length of the meandering conductor 40H can be
set as appropriate to make the maximum value of the characteristic
impedance in the second region 100H larger than the maximum value
of the characteristic impedance in the first region 100S. Thus, the
variation width .DELTA.R1 of the characteristic impedance in the
second region 100H is preferably larger than the variation width
.DELTA.R0 of the characteristic impedance in the first region
100S.
Further, the variation width .DELTA.R1 of the characteristic
impedance in the second region 100H is preferably set to be larger
than the maximum value .DELTA.R0' that the variation width
.DELTA.R0 of the characteristic impedance may take when the first
region 100S is curved or bent.
With such a configuration, even if the first region 100S is curved
or bent and the characteristic impedance in the first region 100S
is varied, the maximum value of the variation width of the
characteristic impedance for the transmission line portion 10 is
the variation width .DELTA.R1 of the characteristic impedance in
the second region 100H.
Thus, the characteristic impedance for the transmission line
portion 10 is hardly varied even if the first region 100S is curved
or bent.
Thus, if the shape of various portions of the transmission line
portion 10 is set so as to obtain a desired characteristic
impedance Z0 with the distribution of the characteristic impedance
in the first region 100S and the characteristic impedance in the
second region 100H taken into consideration in advance, the
characteristic impedance for the transmission line portion 10 is
kept constant without being affected by a curve or a bend of the
first region 100S. Thus, a flat cable with good transmission
characteristics is achieved.
For example, the transmission characteristics are not degraded even
if the flat cable 60 is utilized as curved at the first regions
100S as illustrated in FIGS. 1B and 1C, implementing a flat cable
with good transmission characteristics.
The interval between the second regions 100H along the transmission
direction, that is, the interval ("S" in FIG. 4A) between positions
at which the absolute value of the impedance becomes largest, is
preferably short. If the interval S is short, the frequency of a
standing wave which affects the transmission-frequency
characteristics of the transmission line portion 10 is increased.
Thus, the transmission-frequency characteristics of the
transmission line portion 10 in the frequency band of the
transmission signal are improved by adjusting the interval S to be
short to achieve a high frequency that is distant from the
frequency of the high-frequency signal to be transmitted. That is,
transmission characteristics with a low loss are provided in the
frequency band of the transmission signal.
With the configuration according to the present preferred
embodiment, further, the phase of the high-frequency signal is
rotated by a predetermined phase amount. Thus, the high-frequency
signal is supplied after being adjusted to a more appropriate phase
in the case where the flat cable is connected to a circuit element
with output characteristics that differ in accordance with the
phase such as a high-frequency power amplifier. Thus, the
characteristics (such as transmission signal output
characteristics, for example) of a high-frequency module in which
the flat cable is used are improved.
The connection conductors 50H in the second region 100H discussed
above are preferably larger in diameter than the connection
conductors 50 in the first region 100S. The number of the
connection conductors 50H provided is preferably as large as
possible. As the number of the connection conductors 50H is larger,
the hardness of the second region 100H against a curve is
enhanced.
The thus structured flat cable is manufactured as follows, for
example.
First, a first insulating film to both surfaces of which copper is
affixed and a second insulating film to one surface of which copper
is affixed are prepared.
A first ground conductor 20 is formed by a patterning process at a
portion on the side of the first principal surface of the first
insulating film corresponding to the first region 100S. A first
ground conductor 20H is formed by a patterning process at a portion
on the side of the first principal surface of the first insulating
film corresponding to the second region 100H.
A signal conductor 40 is formed by a patterning process at a
portion on the side of the second principal surface of the first
insulating film corresponding to the first region 100S. A
meandering conductor 40H and third ground conductors 41 are formed
by a patterning process at a portion on the side of the second
principal surface of the first insulating film corresponding to the
second region 100H.
A plurality of sets of the first ground conductors 20 and 20H, the
signal conductor 40, the meandering conductor 40H, and the third
ground conductors 41 are formed and arranged on the first
insulating film.
A second ground conductor 30 is formed by a patterning process at a
portion on the side of the second principal surface of the second
insulating film corresponding to the first region 100S. A second
ground conductor 30H is formed by a patterning process at a portion
on the side of the second principal surface of the second
insulating film corresponding to the second region 100H. A
plurality of the second ground conductors 30 and 30H are formed and
arranged on the second insulating film.
The first insulating film and the second insulating film are
affixed to each other such that the first ground conductor 20 and
the second ground conductor 30 face each other and the first ground
conductor 20H and the second ground conductor 30H face each other.
In this event, the first insulating film and the second insulating
film are affixed to each other such that the signal conductor 40,
the meandering conductor 40H, and the third ground conductors 41
are disposed between the first insulating film and the second
insulating film. Thus, a plurality of complexes in which the first
ground conductors 20 and 20H and the second ground conductors 30
and 30H are formed on both surfaces of a dielectric element
including the signal conductor 40, the meandering conductor 40H,
and the third ground conductors 41 provided at the middle position
in the thickness direction can be obtained.
Individual transmission line portions 10 are cut out from the
complexes. Protective layers 120 and 130 are formed on the
transmission line portions 10. Coaxial connectors 61 are installed
via conversion pedestals 62 at both ends of the transmission line
portion 10 in the longitudinal direction, and on a surface of the
transmission line portion 10 on which the protective layer 130 is
formed.
The flat cable 60 structured as discussed above can be used for the
following portable electronic device. FIG. 5A is a side sectional
view illustrating the configuration of a portable electronic device
according to the first preferred embodiment of the present
invention. FIG. 5B is a plan sectional view illustrating the
configuration of the portable electronic device.
A portable electronic device 1 includes a thin device housing 2.
Circuit boards 3A and 3B and a battery pack 4 are disposed in the
device housing 2. A plurality of IC chips 5 and components 6 are
mounted on surfaces of the circuit boards 3A and 3B. The circuit
boards 3A and 3B and the battery pack 4 are installed in the device
housing 2 such that the battery pack 4 is disposed between the
circuit boards 3A and 3B as the device housing 2 is viewed in plan.
The device housing 2 is preferably as thin as possible, and thus
the gap between the battery pack 4 and the device housing 2 is
extremely narrow in the thickness direction of the device housing
2. Thus, a coaxial cable cannot be disposed in the gap.
However, the flat cable 60 described in the present preferred
embodiment preferably is disposed such that the thickness direction
of the flat cable 60 and the thickness direction of the device
housing 2 coincide with each other to allow the flat cable 60 to
pass between the battery pack 4 and the device housing 2. Thus, the
circuit boards 3A and 3B spaced from each other with the battery
pack 4 disposed in the middle are connected to each other by the
flat cable 60.
Further, even in the case where the position of connection of the
flat cable 60 to the circuit boards 3A and 3B and a surface of the
battery pack 4 for installation of the flat cable 60 are different
in the thickness direction of the device housing 2 and the flat
cable 60 is curved to be connected, a high-frequency signal is
transmitted while suppressing a transmission loss by using the
structure according to the present preferred embodiment.
Next, a flat cable which is a high-frequency transmission line
according to a second preferred embodiment of the present invention
will be described with reference to the drawings. FIG. 6 is an
exploded perspective view illustrating the structure of a second
region of a transmission line portion of the flat cable according
to the second preferred embodiment of the present invention.
A transmission line portion 10a of a flat cable 60a according to
the present preferred embodiment is different from the transmission
line portion 10 described in the first preferred embodiment in the
structure of a second region 100HC, and otherwise preferably is the
same as the transmission line portion 10. Thus, only differences
will be described.
The second region 100HC includes a flat-plate conductor 40HC
provided between the first dielectric layer 111H and the second
dielectric layer 112H. The flat-plate conductor 40HC is arranged to
extend generally over the entire surface of the second region 100HC
as seen along the thickness direction. The flat-plate conductor
40HC is a so-called solidly filled conductor.
A plurality of connection conductors 50H are arranged to connect
between the first ground conductor 20H and the second ground
conductor 30H at positions with no connection to the flat-plate
conductor 40HC.
With such a configuration, the flat-plate conductor 40HC, the first
ground conductor 20H and the second ground conductor 30H, and the
first and second dielectric layers 111H and 112H define and
function as a capacitor connected between the transmission line and
the ground.
Even with such a configuration, a phase adjustment circuit that
rotates the phase of a high-frequency signal is provided.
With such a configuration, the transmission line portion 10a of the
flat cable 60a has the following distribution characteristics of
characteristic impedance along the longitudinal direction. FIG. 7
is a graph illustrating the distribution characteristics of
characteristic impedance along the longitudinal direction of the
transmission line portion 10a of the flat cable 60a according to
the second preferred embodiment of the present invention.
As in the first preferred embodiment, the variation width of the
characteristic impedance, which is the difference between the
maximum value and the minimum value of the characteristic
impedance, in the first region 100S is .DELTA.R0.
In the second region 100HC, a capacitance is generated between the
first ground conductor 20H and the second ground conductor 30H
using the flat-plate conductor 40HC, which enhances the C property.
Thus, the characteristic impedance is greatly reduced compared to
that at the boundary position between the first region 100S and the
second region 200HC to become minimum. Thus, the variation width of
the characteristic impedance, which is the difference between the
maximum value and the minimum value of the characteristic
impedance, in the second region 100HC is .DELTA.R2, which is larger
than the variation width .DELTA.R0 in the first region 100S.
Further, the variation width .DELTA.R2 of the characteristic
impedance in the second region 100HC is preferably set to be larger
than the maximum value .DELTA.R0' that the variation width
.DELTA.R0 of the characteristic impedance may take when the first
region 100S is curved or bent.
With such a configuration, even if the first region 100S is curved
or bent and the characteristic impedance in the first region 100S
is varied, the maximum value of the variation width of the
characteristic impedance for the transmission line portion 10a is
the variation width .DELTA.R2 of the characteristic impedance in
the second region 100HC.
Thus, the characteristic impedance for the transmission line
portion 10a is hardly varied even if the first region 100S is
curved or bent.
Thus, if the shape of various portions of the transmission line
portion 10a is set so as to obtain a desired characteristic
impedance Z0 with the distribution of the characteristic impedance
in the first region 100S and the characteristic impedance in the
second region 100HC taken into consideration in advance, the
characteristic impedance for the transmission line portion 10a can
be kept constant without being affected by a curve or a bend of the
first region 100S. Thus, a flat cable with good transmission
characteristics is provided.
In the configuration according to the present preferred embodiment,
further, the first and second dielectric layers 111H and 112H are
sandwiched by the first ground conductor 20H, the flat-plate
conductor 40HC, and the second ground conductor 30H, which are
solidly filled electrodes, in the thickness direction. Thus, the
second region 100HC is more resistant to being curved in the
thickness direction. Thus, it is more difficult to curve the second
region 100HC, and variations in characteristic impedance in the
second region 100HC are significantly reduced or prevented.
The interval between the second regions 100H along the transmission
direction, that is, the interval ("S" in FIG. 7) between positions
at which the absolute value of the impedance becomes largest, is
preferably short. If the interval S is short, the frequency of a
standing wave which affects the transmission-frequency
characteristics of the transmission line portion 10a is increased.
Thus, the transmission-frequency characteristics of the
transmission line portion 10a in the frequency band of the
transmission signal is improved by adjusting the interval S to be
short to achieve a high frequency that is distant from the
frequency of the high-frequency signal to be transmitted. That is,
transmission characteristics with a low loss are implemented in the
frequency band of the transmission signal.
Next, a flat cable which is a high-frequency transmission line
according to a third preferred embodiment of the present invention
will be described with reference to the drawings. FIG. 8 is an
exploded perspective view illustrating the structure of a second
region of a transmission line portion of the flat cable according
to the third preferred embodiment of the present invention.
A transmission line portion 10b of a flat cable 60b according to
the present preferred embodiment is different from the transmission
line portion 10a described in the second preferred embodiment in
the structure of the second region 100HC and the structure of the
first dielectric layer, and otherwise preferably is the same as the
transmission line portion 10a. Thus, only differences will be
described.
First ground conductors 20Hb1 and 20Hb2 are provided on the first
dielectric layer 111H of the second region 100HC. The first ground
conductors 20Hb1 and 20Hb2 are flat-plate conductors. The first
ground conductors 20Hb1 and 20Hb2 are spaced from each other with a
predetermined gap 200Hb therebetween. In other words, the first
ground conductor located in the second region 100HC is divided at
an intermediate position along the transmission direction.
The first ground conductor 20Hb1 is connected to the elongated
conductors 21 and 22 provided on one of the first dielectric layers
111 connected to the first dielectric layer 111H. The first ground
conductor 20Hb2 is connected to the elongated conductors 21 and 22
provided on the other first dielectric layer 111 connected to the
first dielectric layer 111H.
The first ground conductors 20Hb1 and 20Hb2 face the flat-plate
conductor 40HC with the first dielectric layer 111H interposed
therebetween.
The first ground conductors 20Hb1 and 20Hb2 are connected to the
second ground conductor 30H via the individual connection
conductors 50H. A plurality of connection conductors 50H are
provided at positions with no connection to the flat-plate
conductor 40HC.
With such a configuration, the first ground conductor 20Hb1 and the
second ground conductor 30H constitute a capacitor, the first
ground conductor 20Hb and the second ground conductor 30H
constitute a capacitor, and the flat-plate conductor 40HC and the
second ground conductor 30H constitute a capacitor. The capacitors
define and function as a capacitor connected between the
transmission line and the ground.
Even with such a configuration, functions and effects similar to
those of the preferred embodiments discussed above are achieved. In
the case where the configuration according to the preferred
embodiment is used, the capacitance of the capacitor connected
between the transmission line and the ground is capable of being
adjusted by adjusting the shape of the gap 200Hb, in other words,
by adjusting the shape of the first ground conductors 20Hb1 and
20Hb2.
In the present preferred embodiment, the first ground conductor
preferably is divided. However, the second ground conductor may be
divided.
Next, a flat cable which is a high-frequency transmission line
according to a fourth preferred embodiment will be described with
reference to the drawings. FIG. 9 is an exploded perspective view
illustrating the structure of a second region of a transmission
line portion of the flat cable according to the fourth preferred
embodiment of the present invention.
A transmission line portion 10c of a flat cable 60c according to
the present preferred embodiment is different from the transmission
line portion 10a described in the second preferred embodiment in
the structure of the first dielectric layer and the structure of
the second region 100HC, and otherwise preferably is the same as
the transmission line portion 10a. Thus, only differences will be
described.
The second dielectric layer preferably has a two-layer structure
with dielectric layers 1121 and 1122. The dielectric layer 1121 is
disposed on the side of the first dielectric layer 111. The signal
conductor 40 is located in the first region on the dielectric layer
1121 on the side of the first dielectric layer 111. The flat-plate
conductor 40HC is located in the second region on the dielectric
layer 1121 on the side of the first dielectric layer 111. A
flat-plate conductor 42 is located in the second region on the
dielectric layer 1122 on the side of the dielectric layer 1121. The
flat-plate conductor 42 is arranged so as to face the flat-plate
conductor 40HC over a predetermined area. The flat-plate conductor
42 is connected to the second ground conductor 30H via the
connection conductor 50H.
No conductors (first ground conductors) are provided on the first
dielectric layer 111H of the second region 100HC. The bridge
conductors 23 which connect between the elongated conductors 21 and
22 are provided at end portions, on the side of the second region
100HC, on the first dielectric layer 111 of the first regions 100S
which interpose the second region 100HC.
With such a configuration, the flat-plate conductor 40HC and the
flat-plate conductor 42 (connected to the second ground conductor
30H) constitute a capacitor. The capacitor defines and functions as
a capacitor connected between the transmission line and the
ground.
With such a configuration, the capacitance generated between the
flat-plate conductor 40HC and the second ground conductor is
increased compared to a case where the flat-plate conductor 42 is
not formed. The capacitance is capable of being adjusted by
adjusting the shape of the flat-plate conductor 42. Further, the
capacitance is capable of being adjusted by adjusting the thickness
of the dielectric layer 1121 between the flat-plate conductors 40HC
and 42.
In the present preferred embodiment, the flat-plate conductor 42
and the second ground conductor 30HC are connected to each other by
the connection conductor 50H. However, the flat-plate conductor
40HC and the flat-plate conductor 42 may be connected to each other
by a connection conductor, and the connection conductor between the
flat-plate conductor 42 and the second ground conductor 30HC may be
omitted. In this case, the capacitance is capable of being adjusted
in accordance with the thickness of the dielectric layer 1122.
Next, a flat cable which is a high-frequency transmission line
according to a fifth preferred embodiment will be described with
reference to the drawings. FIG. 10 is an exploded perspective view
illustrating the structure of a second region of a transmission
line portion of the flat cable according to the fifth preferred
embodiment of the present invention.
A transmission line portion 10d of a flat cable 60d according to
the present preferred embodiment is different from the transmission
line portion 10a described in the second preferred embodiment in
the structure of the second region 100HC, and otherwise preferably
is the same as the transmission line portion 10. Thus, only
differences will be described.
The flat-plate conductor 42 is provided on the first dielectric
layer 111H in the second region 100HC. The flat-plate conductor 42
is arranged to extend generally over the entire surface of the
first dielectric layer 111H excluding a region with a predetermined
width along the outer periphery of the first dielectric layer 111H.
The flat-plate conductor 42 is separated from the elongated
conductors 21 and 22 formed on the first dielectric layer 111 of
the first region 100S. A routing conductor 421 is connected to the
flat-plate conductor 42. The routing conductor 421 is provided on
the first dielectric layer 111H of the second region 100 HC.
The bridge conductors 23 which connect between the elongated
conductors 21 and 22 are provided at end portions, on the side of
the second region 100HC, on the first dielectric layer 111 of the
first regions 100S which interpose the second region 100HC.
A flat-plate conductor 40HCd is provided on the second dielectric
layer 112H in the second region 100HC. The flat-plate conductor
40HCd is also arranged to extend generally over the entire surface
of the second dielectric layer 112H excluding a region with a
predetermined width along the outer periphery of the second
dielectric layer 112H. The flat-plate conductor 40HCd is connected
to only the signal conductor 40 formed on one of the first regions
100S, and separated from the signal conductor 40 on the other first
region 100S. The side on which the flat-plate conductor 42 is
separated from the linear conductor 100 is the same as the side on
which the routing conductor 421 is formed on the first dielectric
layer 111H.
The signal conductor 40 on the separated side extends to the second
region 100HC. The signal conductor 40 extending to the second
region 100HC and the routing conductor 421 of the first dielectric
layer 111H are connected to each other by a connection conductor
52.
With such a configuration, the flat-plate conductors 40HCd and 42
constitute a capacitor provided across the first dielectric layer
111H. The flat-plate conductor 40HCd is connected to one of the
signal conductors 40, and the flat-plate conductor is connected to
the other signal conductor 40. Thus, the capacitor defines and
functions as a capacitor connected in series with the signal
transmission line.
Further, a second ground conductor 30Hd of the second region 100HC
is open except for a region with a predetermined width along the
outer periphery discussed above. With such a configuration, the
flat-plate surfaces of the flat-plate conductor 40HCd and the
second ground conductor 30Hd do not face each other. Thus, almost
no capacitive coupling is caused between the flat-plate conductor
40HCd and the second ground conductor 30Hd. Thus, in the case where
only a series capacitor is required, such an opening is preferably
provided. In the case where a parallel capacitor is also required,
an opening is preferably not provided.
Next, a flat cable which is a high-frequency transmission line
according to a sixth preferred embodiment of the present invention
will be described with reference to the drawings. FIG. 11 is an
exploded perspective view illustrating the structure of a second
region of a transmission line portion of the flat cable according
to the sixth preferred embodiment of the present invention.
A transmission line portion 10e of a flat cable 60e according to
the preferred embodiment is different from the transmission line
portion 10a described in the second preferred embodiment in the
structure of the second region 100HC, and otherwise preferably is
the same as the transmission line portion 10a. Thus, only
differences will be described.
A pair of comb-teeth conductors 40HCe1 and 40HCe2 are provided on
the second dielectric layer 112H in the second region 100HC. The
comb-teeth conductors 40HCe1 and 40HCe2 are connected to different
signal conductors 40. The comb-teeth conductors 40HCe1 and 40HCe2
are disposed not to be connected to each other. In other words,
conductive fingers of the comb-teeth conductors 40HCe1 and 40HCe2
are disposed at predetermined intervals in the width direction of
the second dielectric layer 112H.
With such a configuration, a capacitance is generated between the
conductive fingers of the comb-teeth conductors 40HCe1 and 40HCe2
so that the comb-teeth conductors 40HCe1 and 40HCe2 define and
function as a capacitor. The capacitance is generated through
coupling on the second dielectric layer 112H, that is, within an
identical plane, and thus not easily varied under the influence of
a conductor disposed outside the plane.
In the configuration, in addition, the capacitance is determined in
accordance with the length of the conductive fingers provided
opposite to each other, and therefore not affected by the thickness
of the dielectric layer between the conductors constituting the
capacitor. Thus, the design capacitance is achieved reliably and
accurately.
With the configuration, in addition, the shielding performance
against an external electromagnetic field is improved if the
comb-teeth conductors 40HCe1 and 40HCe2 constituting the capacitor
are interposed between the first ground conductor 20H and the
second ground conductor 30H which are solidly filled
conductors.
Next, a flat cable which is a high-frequency transmission line
according to a seventh preferred embodiment of the present
invention will be described with reference to the drawings. FIG. 12
is an exploded perspective view illustrating the structure of a
second region of a transmission line portion of the flat cable
according to the seventh preferred embodiment of the present
invention.
A transmission line portion 10f of a flat cable 60f according to
the present preferred embodiment is different from the transmission
line portion 10c described in the fourth preferred embodiment in
the structure of the first dielectric layer and the structure of
the second region 100HC, and otherwise preferably is the same as
the transmission line portion 10c. Thus, only differences will be
described.
The second dielectric layer preferably has a two-layer structure
with dielectric layers 1121 and 1122. The dielectric layer 1121 is
disposed on the side of the first dielectric layer 111. The signal
conductor 40 is located in the first region 100S on the dielectric
layer 1121 on the side of the first dielectric layer 111.
Flat-plate conductors 40HCf1 and 40HCf2 are located in the second
region 100HC on the dielectric layer 1121 on the side of the first
dielectric layer 111. The flat-plate conductors 40HCf1 and 40HCf2
are separated from each other with a predetermined gap
therebetween. The flat-plate conductors 40HCf1 and 40HCf2 are
connected to different signal conductors 40.
A flat-plate conductor 42 is located in the second region 100HC on
the dielectric layer 1122 on the side of the dielectric layer 1121.
The flat-plate conductor 42 is arranged so as to face the
flat-plate conductors 40HCf1 and 40HCf2 over a predetermined
area.
No conductors (first ground conductors) are provided on the first
dielectric layer 111H of the second region 100HC. The bridge
conductors 23 which connect between the elongated conductors 21 and
22 are provided at end portions, on the side of the second region
100HC, on the first dielectric layer 111 of the first regions 100S
which interpose the second region 100HC.
With such a configuration, the flat-plate conductors 40HCf1 and 42
face each other across the dielectric layer 1121 to constitute a
capacitor. In addition, the flat-plate conductors 40HCf2 and 42
face each other across the dielectric layer 1121 to constitute a
capacitor. Since the flat-plate conductors 40HCf1 and 40HCf2 are
connected to different signal conductors 40, the capacitors define
and function as two capacitors connected in series with the signal
transmission line.
Further, a second ground conductor 30Hf of the second region 100HC
is open except for a region with a predetermined width along the
outer periphery discussed above. With such a configuration, the
flat-plate surfaces of the flat-plate conductor 42 and the second
ground conductor 30Hf do not face each other. Thus, almost no
capacitive coupling is caused between the flat-plate conductor 42
and the second ground conductor 30Hf. Thus, in the case where only
a series capacitor is required, such an opening is preferably
provided. In the case where a parallel capacitor is also required,
an opening is preferably not provided.
In the preferred embodiments discussed above, the second regions
100H and 100HC are wider than the first region 100S. However, the
flat cable may have a constant width as illustrated in FIG. 13.
FIG. 13 is a perspective view illustrating the appearance of a flat
cable with a constant width. As illustrated in FIG. 13, a
transmission line portion 10' of a flat cable 60' includes first
regions 100S and second regions 100H' connected alternately. The
first regions 100S and the second regions 100H' preferably have the
same width as each other. Such a configuration with a constant
width may be adopted if the rigidity of the second regions 100H' is
higher than the rigidity of the first regions 100S.
In the preferred embodiments discussed above, the width of the
opening portion 24 in the first region 100S preferably is constant,
for example. However, the opening portion may be successively
widened from an end portion connected to the bridge conductor
toward the center in the longitudinal direction of the opening
portion. Thus, abrupt variations in characteristic impedance in the
first region are significantly reduced or prevented so as to
further reduce or prevent a transmission loss.
In the preferred embodiments discussed above, the width of the
signal conductor 40 in the first region 100S preferably is
constant, for example. However, the signal conductor may be widened
at a portion facing the opening portion. In this event, the signal
conductor is not widened to such a degree that the signal conductor
overlaps the elongated conductors as the flat cable is seen in the
thickness direction. Thus, the high-frequency resistance of the
signal conductor is reduced to reduce the conductor loss of the
flat cable.
Although not specifically described in the preferred embodiments
discussed above, a single second region may be provided rather than
a plurality thereof. In the case where a plurality of second
regions are provided, the second regions preferably have generally
the same variation width of the characteristic impedance. Thus, the
influence of the characteristic impedance in the second region on
the flat cable is further increased to achieve a further stable
characteristic impedance for the flat cable.
In the preferred embodiments discussed above, a phase adjustment
circuit for the second region is preferably defined by a
distributed constant circuit, for example. However, the phase
adjustment circuit for the second region may be implemented by a
lumped-constant circuit element, that is, a surface mount coil or a
surface mount capacitor. In the case where a surface mount coil is
used, for example, the signal conductor 40 is extended to the
second region. The signal conductor 40 is cut in the second region.
Two lands are provided on a surface of the first dielectric layer
111H, and connected to the two cut ends of the signal conductor 40
by a via conductor or the like. A surface mount coil is mounted to
the two lands.
In the preferred embodiments discussed above, a tri-plate
transmission line in which a signal conductor is disposed between a
first ground conductor and a second ground conductor preferably is
used. However, the configuration discussed above may also be
applied to a microstrip transmission line from which a second
ground conductor has been omitted.
In the preferred embodiments discussed above, the high-frequency
transmission line is preferably in the form of a flat cable.
However, the present invention is not limited to a flat cable. That
is, preferred embodiments of the present invention may be used for
a high-frequency transmission line that constitutes a portion of an
RF circuit board such as an antenna front-end module.
While preferred embodiments of the present invention have been
described above, it is to be understood that variations and
modifications will be apparent to those skilled in the art without
departing from the scope and spirit of the present invention. The
scope of the present invention, therefore, is to be determined
solely by the following claims.
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